feat: snap prepare-image plugins

imagecraft/models/volume.py

@@ -161,6 +161,9 @@ class Role(str, enum.Enum):
     SYSTEM_BOOT = "system-boot"
     """The partition stores the image's boot assets."""
 
+    SYSTEM_SEED = "system-seed"
+    """The partition stores the image's initial seed data used during first boot."""
+
 
 class StructureItem(CraftBaseModel):
     """Structure item of the image."""

imagecraft/plugins/_setup.py

@@ -18,14 +18,20 @@
 from craft_parts.plugins.plugins import PluginType
 
 from .mmdebstrap_plugin import MmdebstrapPlugin
+from .snap_preseed_plugin import SnapPreseedPlugin
+from .uc_prepare_plugin import UcPreparePlugin
 
 
 def get_app_plugins() -> dict[str, PluginType]:
     """Get Imagecraft-specific craft-parts plugins.
 
     :returns: A dict mapping plugin names to plugins
     """
-    return {"mmdebstrap": MmdebstrapPlugin}
+    return {
+        "mmdebstrap": MmdebstrapPlugin,
+        "snap-preseed": SnapPreseedPlugin,
+        "uc-prepare": UcPreparePlugin,
+    }
 
 
 def setup_plugins() -> None:

imagecraft/plugins/_utils.py

@@ -0,0 +1,60 @@
+# This file is part of imagecraft.
+#
+# Copyright 2026 Canonical Ltd.
+#
+# This program is free software: you can redistribute it and/or modify it
+# under the terms of the GNU General Public License version 3, as published
+# by the Free Software Foundation.
+#
+# This program is distributed in the hope that it will be useful, but WITHOUT
+# ANY WARRANTY; without even the implied warranties of MERCHANTABILITY,
+# SATISFACTORY QUALITY, or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+# General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License along
+# with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+"""Shared plugin utilities."""
+
+from craft_application.models.constraints import PROJECT_NAME_COMPILED_REGEX
+
+VALID_RISKS = ["stable", "candidate", "beta", "edge"]
+MAX_LEN = 40
+MAX_CHANNEL_PARTS = 3
+
+
+def validate_snap_refs(snaps: list[str]) -> list[str]:
+    """Validate a list of snap references."""
+    for snap in snaps:
+        if snap.endswith(".snap"):
+            continue
+
+        parts = snap.split("/")
+
+        name = parts[0]
+        if not (len(name) <= MAX_LEN and PROJECT_NAME_COMPILED_REGEX.match(name)):
+            raise ValueError(f"Invalid snap reference {snap}")
+
+        if (channel_parts := parts[1:]) and (
+            len(channel_parts) > 1
+            and not any(p in VALID_RISKS for p in channel_parts)
+            or len(channel_parts) > MAX_CHANNEL_PARTS
+        ):
+            raise ValueError(f"Invalid snap reference {snap}")
+
+    return snaps
+
+
+def resolve_snap(snap: str) -> str:
+    """Resolve a snap reference to the format expected by snap prepare-image.
+
+    If the snap reference contains a channel (e.g. ``name/track/risk``), it is
+    converted to the ``name=track/risk`` form that ``snap prepare-image``
+    expects.  Plain snap names and local ``.snap`` file paths are returned
+    unchanged.
+    """
+    snap = snap.strip()
+    if "/" in snap and not snap.endswith(".snap"):
+        name, channel = snap.split("/", 1)
+        snap = f"{name}={channel}"
+    return snap

imagecraft/plugins/snap_preseed_plugin.py

@@ -0,0 +1,105 @@
+# This file is part of imagecraft.
+#
+# Copyright 2026 Canonical Ltd.
+#
+# This program is free software: you can redistribute it and/or modify it
+# under the terms of the GNU General Public License version 3, as published
+# by the Free Software Foundation.
+#
+# This program is distributed in the hope that it will be useful, but WITHOUT
+# ANY WARRANTY; without even the implied warranties of MERCHANTABILITY,
+# SATISFACTORY QUALITY, or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+# General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License along
+# with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+"""The snap-preseed plugin."""
+
+import shlex
+from typing import Literal, cast
+
+from craft_parts.plugins import Plugin, PluginProperties
+from pydantic import field_validator
+from typing_extensions import override
+
+from ._utils import resolve_snap, validate_snap_refs
+
+
+class SnapPreseedPluginProperties(PluginProperties, frozen=True):
+    """Properties for the 'snap-preseed' plugin."""
+
+    plugin: Literal["snap-preseed"] = "snap-preseed"
+
+    snap_preseed_snaps: list[str]
+    snap_preseed_channel: str | None = None
+    snap_preseed_model_assert: str = ""
+    snap_preseed_validation: Literal["ignore", "enforce"] = "ignore"
+    snap_preseed_assertions: list[str] = []
+    snap_preseed_revisions: str | None = None
+    snap_preseed_write_revisions: str | bool = False
+
+    @field_validator("snap_preseed_snaps")
+    @classmethod
+    def _validate_snap_refs(cls, snaps: list[str]) -> list[str]:
+        return validate_snap_refs(snaps)
+
+
+class SnapPreseedPlugin(Plugin):
+    """Prepare snaps for Ubuntu Classic images using 'snap prepare-image'."""
+
+    properties_class = SnapPreseedPluginProperties
+
+    @override
+    def get_build_snaps(self) -> set[str]:
+        """Return a set of required snaps to install in the build environment."""
+        return set()
+
+    @override
+    def get_build_packages(self) -> set[str]:
+        """Return a set of required packages to install in the build environment."""
+        return set()
+
+    @override
+    def get_build_environment(self) -> dict[str, str]:
+        """Return a dictionary with the environment to use in the build step."""
+        return {}
+
+    @override
+    def get_build_commands(self) -> list[str]:
+        """Return a list of commands to run during the build step."""
+        options = cast(SnapPreseedPluginProperties, self._options)
+        cmd = [
+            "snap",
+            "prepare-image",
+            "--classic",
+            f"--arch={self._part_info.target_arch}",
+            f"--validation={options.snap_preseed_validation}",
+        ]
+        if options.snap_preseed_channel:
+            cmd.append(f"--channel={options.snap_preseed_channel}")
+
+        if options.snap_preseed_revisions:
+            cmd.append(f"--revisions={options.snap_preseed_revisions}")
+
+        if options.snap_preseed_write_revisions:
+            revisions_path = self._part_info.part_install_dir / (
+                "seed.manifest"
+                if isinstance(options.snap_preseed_write_revisions, bool)
+                else options.snap_preseed_write_revisions.lstrip("/")
+            )
+
+            revisions_path.parent.mkdir(parents=True, exist_ok=True)
+            cmd.append(f"--write-revisions={revisions_path}")
+
+        cmd.extend(
+            f"--assert={assertion}" for assertion in options.snap_preseed_assertions
+        )
+
+        cmd.extend(
+            f"--snap={resolve_snap(snap)}" for snap in options.snap_preseed_snaps
+        )
+
+        cmd.append(options.snap_preseed_model_assert)
+        cmd.append(str(self._part_info.part_install_dir))
+        return [shlex.join(cmd)]

imagecraft/plugins/uc_prepare_plugin.py

@@ -0,0 +1,144 @@
+# This file is part of imagecraft.
+#
+# Copyright 2026 Canonical Ltd.
+#
+# This program is free software: you can redistribute it and/or modify it
+# under the terms of the GNU General Public License version 3, as published
+# by the Free Software Foundation.
+#
+# This program is distributed in the hope that it will be useful, but WITHOUT
+# ANY WARRANTY; without even the implied warranties of MERCHANTABILITY,
+# SATISFACTORY QUALITY, or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+# General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License along
+# with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+"""The uc-prepare plugin."""
+
+from typing import Literal, cast
+
+from craft_parts.plugins import Plugin, PluginProperties
+from pydantic import field_validator, model_validator
+from typing_extensions import Self, override
+
+from ._utils import resolve_snap, validate_snap_refs
+
+
+class UcPreparePluginProperties(PluginProperties, frozen=True):
+    """Properties for the uc-prepare plugin."""
+
+    plugin: Literal["uc-prepare"] = "uc-prepare"
+
+    uc_prepare_model_assert: str
+    uc_prepare_snaps: list[str] = []
+    uc_prepare_channel: str | None = None
+    uc_prepare_validation: Literal["ignore", "enforce"] = "ignore"
+    uc_prepare_assertions: list[str] = []
+    uc_prepare_revisions: str | None = None
+    uc_prepare_write_revisions: str | bool = False
+    uc_prepare_preseed: bool = False
+    uc_prepare_preseed_sign_key: str | None = None
+    uc_prepare_apparmor_features_dir: str | None = None
+    uc_prepare_sysfs_overlay: str | None = None
+
+    @model_validator(mode="after")
+    def sign_key_requires_preseed(self) -> Self:
+        """preseed-sign-key requires preseed to be enabled."""
+        if self.uc_prepare_preseed_sign_key and not self.uc_prepare_preseed:
+            raise ValueError(
+                "uc-prepare-preseed-sign-key requires uc-prepare-preseed to be set"
+            )
+        return self
+
+    @model_validator(mode="after")
+    def sysfs_overlay_requires_preseed(self) -> Self:
+        """sysfs-overlay requires preseed to be enabled."""
+        if self.uc_prepare_sysfs_overlay and not self.uc_prepare_preseed:
+            raise ValueError(
+                "uc-prepare-sysfs-overlay requires uc-prepare-preseed to be set"
+            )
+        return self
+
+    @field_validator("uc_prepare_snaps")
+    @classmethod
+    def _validate_snap_refs(cls, snaps: list[str]) -> list[str]:
+        return validate_snap_refs(snaps)
+
+
+class UcPreparePlugin(Plugin):
+    """Prepare snaps for Ubuntu Core using 'snap prepare-image'."""
+
+    properties_class = UcPreparePluginProperties
+
+    @override
+    def get_build_snaps(self) -> set[str]:
+        """Return a set of required snaps to install in the build environment."""
+        return set()
+
+    @override
+    def get_build_packages(self) -> set[str]:
+        """Return a set of required packages to install in the build environment."""
+        options = cast(UcPreparePluginProperties, self._options)
+        if (
+            options.uc_prepare_preseed
+            and self._part_info.host_arch != self._part_info.target_arch
+        ):
+            return {"qemu-user-static"}
+        return set()
+
+    @override
+    def get_build_environment(self) -> dict[str, str]:
+        """Return a dictionary with the environment to use in the build step."""
+        return {}
+
+    @override
+    def get_build_commands(self) -> list[str]:
+        """Return a list of commands to run during the build step."""
+        options = cast(UcPreparePluginProperties, self._options)
+
+        cmd = ["snap", "prepare-image"]
+
+        if options.uc_prepare_preseed:
+            cmd.append("--preseed")
+
+        if options.uc_prepare_preseed_sign_key:
+            cmd.append(f"--preseed-sign-key={options.uc_prepare_preseed_sign_key}")
+
+        if options.uc_prepare_apparmor_features_dir:
+            cmd.append(
+                f"--apparmor-features-dir={options.uc_prepare_apparmor_features_dir}"
+            )
+
+        if options.uc_prepare_sysfs_overlay:
+            cmd.append(f"--sysfs-overlay={options.uc_prepare_sysfs_overlay}")
+
+        cmd.append(f"--validation={options.uc_prepare_validation}")
+
+        if options.uc_prepare_channel:
+            cmd.append(f"--channel={options.uc_prepare_channel}")
+
+        if options.uc_prepare_revisions:
+            cmd.append(f"--revisions={options.uc_prepare_revisions}")
+
+        if options.uc_prepare_write_revisions:
+            revisions_path = self._part_info.part_install_dir / (
+                "seed.manifest"
+                if isinstance(options.uc_prepare_write_revisions, bool)
+                else options.uc_prepare_write_revisions.lstrip("/")
+            )
+
+            revisions_path.parent.mkdir(parents=True, exist_ok=True)
+            cmd.append(f"--write-revisions={revisions_path}")
+
+        cmd.extend(
+            f"--assert={assertion}" for assertion in options.uc_prepare_assertions
+        )
+
+        cmd.extend(f"--snap={resolve_snap(snap)}" for snap in options.uc_prepare_snaps)
+
+        cmd.append(
+            f"{options.uc_prepare_model_assert} {self._part_info.part_install_dir}"
+        )
+
+        return [" ".join(cmd)]

tests/spread/plugins/snap-preseed/imagecraft.yaml

@@ -0,0 +1,35 @@
+name: snap-preseed-test
+version: "0.1"
+summary: Test snap-preseed plugin
+description: Test snap-preseed plugin
+base: bare
+build-base: ubuntu@24.04
+
+platforms:
+  armhf:
+    build-on: [amd64]
+    build-for: [armhf]
+
+volumes:
+  disk:
+    schema: gpt
+    structure:
+      - name: rootfs
+        role: system-data
+        type: 0FC63DAF-8483-4772-8E79-3D69D8477DE4
+        filesystem: ext4
+        filesystem-label: writable
+        size: 2G
+
+filesystems:
+  default:
+    - mount: /
+      device: (volume/disk/rootfs)
+
+parts:
+  snaps:
+    plugin: snap-preseed
+    snap-preseed-snaps:
+      - hello-world/latest/stable
+    organize:
+      "var/*": (overlay)/var/

tests/spread/plugins/snap-preseed/task.yaml

@@ -0,0 +1,19 @@
+summary: Test snap-preseed plugin
+
+systems: [ubuntu-24.04-64]
+
+execute: |
+  imagecraft pack --verbose --destructive-mode
+
+  test -f disk.img
+
+  test -d prime/var/lib/snapd/seed/
+  test -f prime/var/lib/snapd/seed/snaps/hello-world_*.snap
+  test -f prime/var/lib/snapd/seed/snaps/core_*.snap
+
+  unsquashfs -d core-snap prime/var/lib/snapd/seed/snaps/core_*.snap --extract-file meta/snap.yaml
+  grep -q "armhf" core-snap/meta/snap.yaml
+
+restore: |
+  rm -rf disk.img core-snap
+  imagecraft clean --destructive-mode